'568 



KNOWER. 



Stage P. Completion of " revolution." Dorsal growth of body-walls. Tracheal 

 stigmata, /r. Dorsal organ, d.o., the retracted remnants of embryonic 

 membranes. 

 " R. Closure of body-walls on the mid-dorsal line complete. Dorsal organ 

 has disappeared within yolk-mass, which is now enclosed in mid- 

 gut. Ventral ganglia shown. As compared with the preceding 

 stage, P, this is more truly an optical section, not showing the 

 body-walls except along the boundaries of the body. 



